What is heat? Heat is the energy needed to change the temperature of 1 g of a substance by 1°C.
O Heat is the average kinetic energy of the particles of a substance.
Heat is the total energy of a substance due to the movement of its particles.
Heat is the energy that flows between two substances of different temperatures.

heat is the total energy of a substance due to the movements of its particles.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.